I put a different viscosity oil on my car than the one it had can this affect it?

Question

i put a quart of 20w-50 oil on my car and the one in the engine is either 10w-30 or 10w-40. can this make a difference on how the oil rises up to the engine and does it become thicker? what happens

Answer 1

Yes.  If a heavier oil is used in the engine other than what the manufacturer specifies it will cause drag on the crankshaft and other moving parts.  This will result in decreased fuel efficiency.